Q. Explain working of Ammeter?
In order to measure the current through a wire or line of a circuit, an ammeter is connected in series with the line. A practical ammeter can usually be modeled as a series combination of an ideal ammeter and an internal resistance RI. The potential difference between the two terminals of an ideal ammeter is zero, which corresponds to zero internal resistance. There are what are known as dc ammeters and ac ammeters. An ac ammeter usually measures the rms value of the time-varying current. Note that for the ammeter to be inserted for measuring current, the circuit has to be broken, whereas for the voltmeter to be connected for measuring voltage, the circuit need not be disassembled.
Multimeters that measure multiple ranges of voltage and current are available in practice. Ohmmeters measure the dc resistance by the use of Ohm's law. A multimeter with scales for volts, ohms, and milliamperes is known as VOM. An ohmmeter should not be used to measure the resistance of an electronic component that might be damaged by the sensing current.